To effectively interpret the vast amount of visual information available in the world using only limited neural resources, the human visual system must continually modify how it allocates neural resources to processing of visual stimuli. Perhaps the two most important ways the nervous system accomplishes this are through adaptation and attention. Adaptation can serve to make neurons most sensitive to the current statistics of scenes being viewed. Attention can covertly shift neural resources without moving the eyes to process stimuli of interest with faster speeds and higher accuracy. The present proposal seeks to use functional magnetic resonance imaging in humans to examine how neural sensitivity to image contrast changes with adaptation and attention, and to determine if any observed changes can account for behavioral performance. Furthermore, we will pit adaptation against attention to see if the two processes share similar underlying mechanisms. As there are as many as 2 million American children affected by disorders of attention such as attention deficit hyperactivity disorder (ADHD), it is of fundamental importance to fully understand the underpinnings of human attentional processes. [unreadable] [unreadable]